using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using System.Collections.Generic;

namespace SemiColinGames {
  public static class Debug {
    struct DebugRect {
      public Rectangle Rect;
      public Color Color;

      public DebugRect(Rectangle rect, Color color) {
        Rect = rect;
        Color = color;
      }
    }

    struct DebugLine {
      public Point Start;
      public Point End;
      public Color Color;

      public DebugLine(Point start, Point end, Color color) {
        Start = start;
        End = end;
        Color = color;
      }
    }

    public static bool Enabled = false;
    // This is a LinkedList instead of a List because SetFpsText() adds to its front.
    static readonly LinkedList<string> toasts = new LinkedList<string>();
    // Lines in excess of MAX_LINES get dropped on the floor.
    const int MAX_LINES = 2000;
    const int MAX_LINE_VERTICES = MAX_LINES * 2;

    static int lineIdx = 0;
    static VertexPositionColor[] lineVertices;
    static VertexBuffer vertexBuffer;

    [System.Diagnostics.Conditional("DEBUG")]
    public static void Initialize(GraphicsDevice graphics) {
      lineVertices = new VertexPositionColor[MAX_LINE_VERTICES];
      vertexBuffer?.Dispose();
      vertexBuffer = new VertexBuffer(
          graphics, typeof(VertexPositionColor), MAX_LINE_VERTICES, BufferUsage.WriteOnly);
    }

    [System.Diagnostics.Conditional("DEBUG")]
    public static void WriteLine(string s) {
      System.Diagnostics.Debug.WriteLine(s);
    }

    [System.Diagnostics.Conditional("DEBUG")]
    public static void WriteLine(string s, params object[] args) {
      System.Diagnostics.Debug.WriteLine(s, args);
    }

    [System.Diagnostics.Conditional("DEBUG")]
    public static void Clear(bool paused) {
      toasts.Clear();
      if (!paused) {
        lineIdx = 0;
      }
    }

    [System.Diagnostics.Conditional("DEBUG")]
    public static void AddToast(string s) {
      toasts.AddLast(s);
    }

    // FPS text is always displayed as the first toast (if set).
    [System.Diagnostics.Conditional("DEBUG")]
    public static void SetFpsText(string s) {
      toasts.AddFirst(s);
    }

    [System.Diagnostics.Conditional("DEBUG")]
    public static void AddRect(Rectangle rect, Color color) {
      AddLine(rect.Left, rect.Top + 1, rect.Right, rect.Top + 1, color);
      AddLine(rect.Left + 1, rect.Top + 1, rect.Left + 1, rect.Bottom, color);
      AddLine(rect.Right, rect.Top + 1, rect.Right, rect.Bottom, color);
      AddLine(rect.Left + 1, rect.Bottom, rect.Right, rect.Bottom, color);
    }

    [System.Diagnostics.Conditional("DEBUG")]
    public static void AddRect(AABB box, Color color) {
      Rectangle rect = new Rectangle(
          (int) (box.Position.X - box.HalfSize.X), (int) (box.Position.Y - box.HalfSize.Y),
          (int) (box.HalfSize.X * 2), (int) (box.HalfSize.Y * 2));
      AddRect(rect, color);
    }

    [System.Diagnostics.Conditional("DEBUG")]
    public static void AddLine(Point start, Point end, Color color) {
      if (lineIdx >= MAX_LINE_VERTICES) {
        return;
      }
      lineVertices[lineIdx] = new VertexPositionColor(new Vector3(start.X, start.Y, 0), color);
      lineVertices[lineIdx + 1] = new VertexPositionColor(new Vector3(end.X, end.Y, 0), color);
      lineIdx += 2;
    }

    [System.Diagnostics.Conditional("DEBUG")]
    public static void AddLine(int p1x, int p1y, int p2x, int p2y, Color color) {
      AddLine(new Point(p1x, p1y), new Point(p2x, p2y), color);
    }

    [System.Diagnostics.Conditional("DEBUG")]
    public static void AddLine(Vector2 start, Vector2 end, Color color) {
      AddLine(start.ToPoint(), end.ToPoint(), color);
    }

    [System.Diagnostics.Conditional("DEBUG")]
    public static void DrawToasts(SpriteBatch spriteBatch) {
      if (!Enabled) {
        return;
      }
      // UI should start at least 48px from the left edge of the screen and 27 from the top, as per:
      // https://docs.microsoft.com/en-us/windows/uwp/design/devices/designing-for-tv#tv-safe-area
      // Can test this on actual Xbox via:
      // Settings > Launch Settings > Display & Sound > Resolution > 720p.
      int y = 27;
      foreach (var toast in toasts) {
        spriteBatch.DrawString(Textures.DebugFont, toast, new Vector2(48, y), Color.Teal);
        y += 30;
      }
    }

    [System.Diagnostics.Conditional("DEBUG")]
    public static void Draw(GraphicsDevice graphics, BasicEffect lightingEffect) {
      if (!Enabled) {
        return;
      }
      if (lineIdx == 0) {
        return;
      }

      graphics.SetVertexBuffer(vertexBuffer);
      vertexBuffer.SetData(lineVertices);
      foreach (EffectPass pass in lightingEffect.CurrentTechnique.Passes) {
        pass.Apply();
        graphics.DrawPrimitives(PrimitiveType.LineList, 0, lineIdx / 2);
      }
    }
  }
}